hello, i have a 98 mitsubishi eclipse which has a forklift motor in it. but no batteries, motor controller or electronics.
I have been collecting 18650 cells for months and have about 1000, which i am going through and testing.
Now i did a bit of math, estimating my batteries need to be able to provide 400Amps and so i will need at least 80 cells in parallel. my motor controller claims a 300A max, but i think headroom would be good and create less strain on the batteries.
Voltage can be whatever i want it to be, my motor controller which is on the way, claims to have a working voltage between 25-200volts. To have speed and acceleration i am thinking i should shoot for near 120v. Which would mean i need 32 cells in series. so i need at least 2560 cells minimum to have a completed car battery.
Assuming all these cells are usable to 2AH. i would have 18,944Watt Hours. unless i did my math wrong. That would give me a 120Volt 160AH battery right?
assuming i can get 1 mile per 300WH, i could about 63 miles on a full charge.

253Lbs of batteries alone without holders/wire/ect.

While this doesn't sound too bad to me, I am still far from having that many cells which are all clean and healthy. And the computer stores i have been getting my cells from are wanting to charge me between $1-3 per laptop battery. i would say on average each battery has between 6-9 cells. so i would have to spend about $1000. to get the rest of the laptop batteries i need, assuming most of the cells are good.

I have been following jehugarcia on youtube and he reccomended these batteries https://us2.campaign-archive.com/?e=&u=e...f8a253f520
for the price it appears to be a deal. Except for the AH rating, at 60AH they are much smaller than the 160AH i would have with 80x18650 in parallel.
The problem with that approach is the minimum order quantity is 9 batteries, + freight/S&H $1785. per 9 batteries, Unless i want to use this car for very short distances i would need more capacity. So to get more AH than the 18650 cells i would need 21 batteries in a 7s3p configuration. And 3 pallets = $5355.
and because each battery is about the size of a small car battery, i might run into the issue of how to fit 21 of them into the car. Also, they would weigh approx 518Lbs. for 23,100WH
And, maybe just as problematic is they don't list specific information about the working voltage range of each battery. and they do not have built in BMS or protection, so i would still need to come up with some way to charge them.

So right now, the 18650 appears to be the more affordable option. At least if i stick with lithium cells.

But there is also the big complication of how will i charge and balance all of these cells.
i have been looking around hoping to find some kind of DIY balancing circuit that could handle something like this with no luck.

Thanks.
It looks like i may have to look up all these cells individually, I had only looked up several of these cells, one in particular is ICR18650H. molicel brand.
2200mAh, max discharge current 5A.
I was basing my math off of that rating.
I have about 250 of these cells all brand new, i pulled from server ups batteries. But all the others are laptop cells.

I suppose i will keep collecting cells and testing them.
on the bright side 300p30s would give 71,040 WH. = 236Miles or so.
I don't think that many of the powerwalls on this site are even 71KWH. hmmm..

300s seems a little excessive, that is more than 1.11kV nomimal. At 400A this is 444kW. I guess a forklift motor isn't the best thing to start with as it surely is setup for maximum power and low speed? Most EV systems run on anything between 150V and 300V or so, depending on their size, with a proper, purpose made motor.

If you were to build a battery for this, as daromer said, you'll be looking at 400p at least. In my opinion even a bit more, like 500p. Needless to say that this is impossible, 300s500p is 150k cells and weighs about 7000kg.
Tesla uses a 16x 6s74p setup for the 85kWh battery with brand new cells and make sure they don't get stressed so much. If you start with already used cells, puhh, its tough if you are looking at that levels of power. They can get away with a 74p setup but sadly you can't with used cells. And you want them to last, right? It's no good if you have to rebuilt your battery twice a year.

(11-13-2017, 11:37 PM)DarkRaven Wrote: 300s seems a little excessive, that is more than 1.11kV nomimal. At 400A this is 444kW. I guess a forklift motor isn't the best thing to start with as it surely is setup for maximum power and low speed? Most EV systems run on anything between 150V and 300V or so, depending on their size, with a proper, purpose made motor.

If you were to build a battery for this, as daromer said, you'll be looking at 400p at least. In my opinion even a bit more, like 500p. Needless to say that this is impossible, 300s500p is 150k cells and weighs about 7000kg.
Tesla uses a 16x 6s74p setup for the 85kWh battery with brand new cells and make sure they don't get stressed so much. If you start with already used cells, puhh, its tough if you are looking at that levels of power. They can get away with a 74p setup but sadly you can't with used cells. And you want them to last, right? It's no good if you have to rebuilt your battery twice a year.

not 300s.. 30s. maybe 34s x500p =17k cells. but that is still too much weight over 1600lbs.

but i have some good news. i contacted a few recycling centers and found one which may be able to help. i am supposed to call back Monday to speak with a gentlemen regarding prices of batteries. apparently they have lithium automotive batteries and laptop batteries.
so i will try and weigh my options there and see what i can come up with.

if i go another route i suppose all these 18650 batteries i have collected so far can go towards my other projects, 48v go kart and E-Bike among a few other things.

less V- volts more A-Amps, more volts less amps. this is the math
whats you motor rated at ? Don't forget the peak power, or short burst that it needs. Start with this.
What efficiency is Controller ? You have to add all the conversion losses. That is the power that you have to provide, but you loose it in process. 80x in parallel add up only to 80A drain recommended at 1A drain for each cell.
You can use high drain batteries from power equipment, like battery powered drills, saws ect. They usually have 1500mAh batteries, but can be used for 10A drains for each cell. This way you get ~14kWh 120V 80-800A (10A max from 1 cell) battery. If you need 400A in 120V pack you'll need at least 300 cells in parallel (1.4A for cell ) laptop batteries.

120V 300A = 200V 180A power have to stay constant. When lowering the Voltage you will have to provide even more power to get the same output power

I'm working towards building a 18650 based vehicle battery as well. My needs are very basic as the vehicle would be a town commuter and have a range requirement something like 50km, and a top speed of 70km/hr. I'm wondering if I would still need 300p cells for this service, Would it be possible, if I'm willing to sacrifice acceleration, to go with 150p and limit current with the controller?